In the manufacture of integrated circuits it is sometimes desirable to create an anti-fuse structure. The operation of an anti-fuse is opposite to the operation of a fuse. When a fuse is operationally activated, the resistance of the fuse decreases from a high level of resistance to a low level of resistance. When an anti-fuse is operationally activated, the resistance of the anti-fuse increases from a low level of resistance to a high level of resistance.
Examples of prior art anti-fuse structures and methods of their manufacture are described in U.S. Pat. No. 6,440,781 and in U.S. Pat. No. 6,563,189. These patents describe prior art anti-fuse structures that are used in conjunction with a tungsten plug metallization process. These patents describe prior art methods that employ a tungsten etchback process and a high temperature aluminum deposition to enable a good contact fill. The anti-fuse manufacturing processes that are described in the prior art are compatible with a back end process flow that uses a tungsten plug metallization process.
Further progress of integrated circuit technology has made it clear that prior art anti-fuses and the methods of their manufacture are not convenient for use in advanced aluminum backend technology nodes. Specifically, the prior art structures and methods are not convenient for use with advanced aluminum backend technology nodes of 0.35 micron size or 0.25 micron size. This makes it difficult to port an integrated circuit device design from an older factory (that uses the prior art technology) to a newer factory (that uses advanced aluminum backend technology nodes). Use of the prior art structures and methods in a newer factory would require a radical redesign of the integrated circuit device or the use of outdated process equipment in the newer factory.
Therefore, there is a need in the art for an improved anti-fuse structure and method of manufacture. There is a need in the art for an improved anti-fuse structure and method of manufacture that allows the porting of an integrated circuit device design from an older technology. There is a need in the art for an improved anti-fuse structure and method of manufacture that is compatible with advanced aluminum backend technology nodes. There is a need in the art for an improved anti-fuse structure and method of manufacture that can remedy the above described deficiencies of prior art anti-fuse technology.
In an advantageous embodiment of the system and method of the present invention, a tungsten plug is formed in a dielectric layer, that overlies a portion of P type silicon and an adjacent portion of N type silicon. The dielectric layer is etched to create a first anti-fuse contact opening down to the underlying P type silicon and a second anti-fuse contact opening down to the underlying N type silicon. A metal layer is then deposited over the tungsten plug and over the dielectric layer. The metal layer is then etched to form a first anti-fuse metal contact in the first anti-fuse contact opening and to form a second anti-fuse metal contact in the second anti-fuse contact opening.
A bias voltage is applied to the first and second anti-fuse metal contacts to activate the anti-fuse. The application of the bias voltage creates an electrically conductive path from the first anti-fuse metal contact through the underlying P type silicon and through the underlying N type silicon to the second anti-fuse metal contact.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.